A man runs as emergency sirens sound during a severe storm over downtown Dallas in December. The sirens went off again just before midnight Friday, but this time the cause was apparently hackers, authorities say. LM OteroThe Associated Press file

A man runs as emergency sirens sound during a severe storm over downtown Dallas in December. The sirens went off again just before midnight Friday, but this time the cause was apparently hackers, authorities say. LM OteroThe Associated Press file

Not so silent night: Dallas emergency siren system hacked

A city emergency alert system in Dallas was hacked overnight, resulting in 156 sirens sporadically sounding for about an hour and a half and forcing officials to shut down the system, authorities said Saturday.

The person or people responsible were able to hack into a part of the system that was communicating with all 156 of the city’s sirens, Rocky Vaz, who heads the city’s Office of Emergency Management, said at a news conference.

He said his office eventually had to shut down the system, which is used to alert people to shelter indoors during severe weather. Technicians are trying to determine how to bring the system back online without the risk of it being hacked again, he said. In the meantime, the public has access to other alert systems, including reverse 911.

The sirens were activated at 11:42 p.m. on Friday. Officials deactivated the entire system by 1:17 a.m. Saturday. Vaz said the sirens went through about 15 cycles of a 90-second siren activation.

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“We shut it down as quickly as we could, taking into consideration all of the precautions and protocols we had to take to make sure that we were not compromising our 156 siren system,” he said.

City spokeswoman Sana Syed said investigators believe the hack came from the Dallas area. Vaz said city officials have asked the Federal Communications Commission for help in determining who was behind the hack. He said police were not involved yet.

“We can’t talk a whole lot about the hack itself, because obviously we don’t want this to happen again,” Syed said.